What is Variable in JAVA ?
- It is a storage space which is used to store data just like a container or box.
- It's value may be changed.
- It always contains last value stored to it.
- It is always declared with data type.
For Example Variable Declaration
int rollno;
float marks;
char grade;
- Here:- rollno is a variable of type int, marks is a variable of type float and grade is a variable of type char.
Variable Initialization
- We can initialize a variable at the time of declaration of variable or after declaration.
int rollno=201;
float marks=97.77;
char grade='A';
- Here :- 201 is the value of rollno,85.6 is the value of marks and A is the value of grade. Character value is always written in single quotes.
Other method of variable Initialization
- We can also initialize a variable after the time of declaration of variable.
int rollno;
float marks;
char grade;
rollno=201;
marks=85.6;
grade='A';
Rules to define a variable
- The first letter of a variable should be alphabet or underscore(_).
- The first letter of variable should not be digit.
- After first character it may be combination of alphabets and digits.
- Back spaces are not allowed in variable name.
- Variable name should not be a keyword.
Types of Variable
- Local Variable
- Instance Variable
- Static Variable
Local Variable:-
- A variable declared inside the body of the method or constructor or block is called local variable.
- Local variable can be used only inside that method/function in which it is declared.
- A local variable can be a static variable.
//Q1. Sum Of Two variable
class Tech369kk
{
public void add()
{
int x, y=10,z=20; //declaring local variable
x=y+z;
System.out.println("Add="+x);
}
public static void main(String[] args)
{
Tech369kk obj=new Tech369kk();
obj.add();
}
}
******Output:***** Add= 30
Instance Variable:-
- A variable which is declared inside a class but outside the body of the method or constructor or block is called instance variable.
- Instance variable can be used anywhere in the program.
class Easy
{
//these instance variabe can be used
int x,y=30,z=20;
public void add()
{
x=y+z;//accessing instance variable
System.out.println("Add="+x);
}
public void sub()
{
x=y-z;//accessing instance variable
System.out.println("Sub="+x);
}
public void mul()
{
x=y*z;//accessing instance variable
System.out.println("Mul="+x);
}
public static void main(String[] args)
{
Easy obj=new Easy();
obj.add();
obj.sub();
obj.mul();
}
}
******Output:*****
Add= 30
Sub= 10
Mul= 600
Static Variable:-
- A variable which is declared with static keyword, inside a class but outside the body of the method or constructor or block is called static variable.
- Static variable is stored in the static memory for permanently.
- Static variables are created when the program starts and destroyed when the program stops.
- Static variable can be called by class name directly.
// Q3. find static keywords in java
class Statt
{
//declaring static variable
static String text="I Hope Clear your Doubts in Java Variable.";
public static void main(String[] args)
{
System.out.println(Statt.text);
}
}
******Output:*****
I Hope Clear your Doubts in Java Variable
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